<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    div {
      width: 100px;
      height: 100px;
      background: url(xxx.png) no-repeat;
      animation: run 1s;
      animation-timing-function: steps(1);
    }

    @keyframes run {
      0% {
        background-position: 0 0;
      }

      50% {
        width: 100px 0;
      }

      100% {
        width: 200px 0;
      }
    }
  </style>

</head>

<body>
  <div></div>
</body>

</html>